An updated WebmasterWorld thread has new reports of such scams. MCC is the higher level AdWords accounts for those who manage campaigns for clients. It is called the My Client Center, and if broken into, more than just one account can be affected.

One person reported:

I got one today. It said that Google's servers had crashed and that I should check to see if my ads were running and click on the link to confirm they were working 100%.

It had me fooled for about 2 seconds. Funny to imagine that Google wouldn't know their own ads were showing and that you would manually need to confirm by clicking a link.

But the email starts with the the phrase "Your account has stopped showing ads." so I can imagine it sending some people into a panic.